1. Field of the Invention
The present invention relates to an electrochemical electrode device.
Such electrode devices include i.e. electrochemical reference electrode devices and so-called combination electrode devices, the latter comprising in one and the same device a measuring part and a reference part.
2. Description of the Prior Art
Very often such electrochemical electrode devices comprise a tubular member essentially sealed at its bottom end so as to establish a container for an inner liquid. The other end of the tubular member is normally closed by a cap member including means for electrically connecting a reference member arranged within the tubular member, to an external conductor or cable.
As far as reference electrode devices and combination electrode devices are concerned, liquid junction means, i.e. a porous plug, a strand or bundle of fibres, such as glass or plastics fibres, or the like should be provided in the above-mentioned closure for establishing electrical contact between the inner liquid and the liquid into which the electrode device is inserted when used. The inner liquid or salt bridge solution is an electrolyte forming a slat-bridge between the liquid junction and an inner reference member located within said tubular member. Usually, the salt bridge solution is a more or less saturated potassium chloride solution and the viscosity of the salt bridge solution may be adjusted by means of gelation agents.
In some cases, it is preferred to use a salt bridge liquid having such low visocity that the liquid may seep through the liquid junction means, whereby a self-cleaning effect of the liquid junction means is obtained. In other cases it is desirable to use a more viscous salt bridge liquid or gel so as to prevent the sample being measured from contamination by seeping salt bridge liquid.
In known electrochemical electrode devices of the type described above, the upper part of the cylindrical wall of the tubular member may be provided with a refill opening which is closed by means of a removable resilient plug extending radially outwardly from the outer cylindrical surface of the tubular member, a rubber hose surrounding the tubular member and being slidable in the axial direction thereof, or the like. This opening makes it possible to refill the tubular member with salt solution so as to replace solution in the tubular member with a different type, for example a more viscous liquid or a gel.
When the refill opening is defined in the cylindrical wall of the tubular member, it may be difficult to completely fill the inner space of the tubular member with liquid or gel, while the electrode device is held in its upright measuring position. The consequent air volume within the tubular member may cause a certain "noise" which may interfere with the potential obtained by the electrode device. Normally, the cap member surrounds the adjacent end of the tubular member so as to form an annular abutment shoulder. The tubular member of the electrode device may then be inserted through an opening in a horizontal wall or panel and be retained in position--for example its measuring or storage position--by engagement between the annular shoulder and the upper surface of the wall or panel. However, a removable stopper projecting radially outwardly from the tubular may interfere with the insertion of the tubular member through the opening defined in the said panel or wall. Furthermore, a refill opening defined in the cylindrical wall of the tubular member does not make it possible to introduce liquid or gel into and/or remove liquid or gel from the electrode device while the device is in an upright position of use.
U.S. Pat. Nos. 3,145,158 and 3,434,953 disclose electrochemical electrode devices in which a refill passage is formed in a cap member closing the upper end of a tubular member. The refill passage extends from an enlarged opening in an upper surface part of the cap member to the inner space of the tubular member. The enlarged opening of the passage is then closed by means of a removable stopper extending from the upper surface part of the cap member, or the enlarged opening may have internal threads which may cooperate with the threads of a screw serving as a removable closure member.